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This was the first of the polyethylenes to be developed. It is the least expensive, most flexible and has good clarity in film form. However, it has low temperature impact resistance and the least heat resistance with a maximum service temperature of 160° to 180°F. Although it is chemical resistant, it can be attacked by strong oxidizing acids. It is also susceptible to stress cracking, especially by detergents, but some copolymers of LDPE are available with stress cracking resistance.
Linear low-density PE (LLDPE) has better impact, tear, heat-seal strengths and environmental stress crack resistance than either LDPE or HDPE. While LLDPE is used mainly for film applications, it can be injected rotational, or blow molded. |
| This standard grade polyethylene film is used mainly for interior signage. The main usage for this film is tight tolerance printing. This film was specially formulated for improved performance for the following characteristics: low shrink, lay flat performance, and corona treatment. The primary advantage for using this film is that preshrinking of this film is not needed so handling of film is greatly reduced. The Poly-Print Plus has been a valuable asset to the 4-color process printer because of the tighter registration tolerance and less handling. This material has a low slip level (> .5 COF) and a high treat level not to be lower than 40 dynes.
Poly Print Plus is also available in colors, call for details. |
 Materials Properties |
MSDS Sheet |
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| This is the premium of all of the polyethylene banner films. It is a co-extruded film that actually consists of three layers of film, two white outer skins surrounding a black core. This film was developed for the ability to print on both sides of the film. It has a consistent corona treatment on both surfaces, a high dyne level and, with NO shadowing through the material creating a product that is 100% opaque. This creates a very stable, highly printable product. Strata-Print II has been printed by screen printing, lithography and 4-color process with great precision and accuracy. The three layers of film help create a tear strength for your outdoor applications. |
| Materials Properties |
MSDS Sheet |
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| Corona treating can be affected by multiple factors at the time of print. Factors such as humidity, temperature, and length of storage will cause dyne levels to drop. In addition, requested gauge and additives, and initial treat level during production will affect the rate and amount by which the dyne level will fall. These factors, along with the rate of production, will also affect achievable dyne level of the material. Following is a brief summary of what the corona treating process actually entails.
The corona treating process transforms the surface molecules of the sheet, oxidizing them (adding electrons). This increases the surface tension (also known as surface energy, wetting tension, or wet ability) of the substrate.
To illustrate the roles of surface tension and surface energy, we can look at the phenomenon of water "beading up" on the hood of a freshly waxed car. The surface tension of the water (70-73 dynes/sq. cm) causes it to form small, tall beads because the wax has lowered the surface energy of the car, preventing the water from spreading out and wetting the hood. If the hood were unwaxed and oxidized, the surface energy of the finish would be greater than the surface tension of the water, so the water would wet the paint.
There are three common methods to test surface tension or wet ability of plastics. The easiest to use and the least accurate is the dyne pen or marker method. If the surface tension of the material is compatible with the ink in the pen, the pen can "write" on the plastic. In the process of this writing, however, the pen picks up contaminants from the surface of the plastic, such as dust and oils. These pens can quickly dry out, concentrating the ink and changing its surface tension.
Another method is the calibrated solution method. This involves applying a calibrated solution to the material with a sterile applicator. If the solution beads upon two seconds, the surface tension of the material matches that of the solution. The surface tension reading can be affected by contamination of the fluid, caused by not using a new applicator for each fluid application and the fluid can quickly evaporate if the cap is left off or is not tightly closed. There is a high potential for inaccuracy in the use of this method. In recent testing conducted by the Flexible Packaging Association technical committee, the range of dyne solution measurements of identical material taken by different labs varied by as much as 15 dyne/sq. cm.
The contact angle meter method of surface tension measurement has been designed to eliminate the vagaries of the dyne pen and the calibrated solution methods. A drop of double-distilled, ultrapure water is applied in a very precise amount by pipettor to the surface of the sheet. Using the half-angle measurement method, the angle from the apex of the drop to the surface of the material is the contact angel with the material. A lower contact angle means that the drop is flatter, indicating a higher surface tension on the surface of the material. Surface tension on a substrate can be determined to within +/- dyne/cm. The benefits of the contact angle meter method include a high level of repeatability and accuracy, easy correlation with dynes/cm, data for statistical process control, and the elimination of judgment calls.
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